Generally, using a conventional user computer system, the user installs a software program in a storage device. The conventional user computer system reads the primitive codes of the software program from a CD-ROM, a diskette or a server computer system. The primitive codes of the software program are stored in a system directory, e.g., a Microsoft Windows™ directory in a Microsoft Windows™ system provided by Microsoft Corporation, and a user directory. The system directory and the user directory have path information associated with the software program files. For example, the software program files may be made up of a main executable file, auxiliary executable files, registry files and other files, including *.dll and *.hlp files, in a Windows™ operating system.
The conventional user computer system needs a large storage space to store the desirable software programs in the storage device. In the case where the conventional user computer system employs various software programs, the conventional user computer system should install the various software programs. Also, in case where the desirable software program is upgraded or updated, the upgraded or updated software program should be installed in the conventional user computer system.
Typically, the conventional user computer system copies or downloads software program files from the server computer system as a remote computer system in order to execute a software program. At execution time, the conventional user computer system may need a specific software program file in addition to the copied or downloaded software program files. If the conventional user computer system does not have the specific program file, the conventional user computer system can not execute the software program.